Process of purifying gases



Patented July 28 1931 mme sTArss PATENT oFFicE WILBERT .7 HUFF Ann cimnnns eon-non MILBOURNE, or BALTIMORE, MARY A D;

' sari) MILBOUBNE ASSIGNOR TO SAID HUEF PROCESS OF PURIFYING- GASES No Drawing. Application filed July 17,

by means of iron oxide is necessary to cause the hydrogen sulfide to react with iron oxide to form iron sulfide. This is indicated by means of the following chemical equation: (FromlVlorgan, Manufactured Gas, Vol. 1, page 430) In order to render the process economic it isnecessary to revivify the iron oxide.- This reaction is indicated by the following equation:

The revivification has been accomplished by removing the oxide from the purifying box and spreading it out in the air, or air has been admitted to the gases undergoing purification in order to permit continuous fouling and revivification. The second process is generally known as revivification in situ.

While the above indicated processes appear very simple and have been carried out in technical practice for a great many years, the operation is accompanied by some uncertainties and dii'liculties. Thus at times it is found that a box of iron oxide which has never been used before fails to remove completely all the hydrogen sulfide when first placed in operation. After a time, however, for no cause readily apparent to the operator, this condition changes, the eficiency of the oxide improves, and the removal of hydrogen sulfide becomes complete. At other times a box which has'been in use only a short time loses its efiiciency and no longer gives a satisfactory removal ofhydrogen sulfide. VThis last has often led to the premature removal of the iron oxide from the box, thus entailing increased expense.

We have found that these faulty operations are associated with improper moisture 1929. Serial no. 379,052

conditions in the oxide, and thatthe role of water vapor in these reactions is very important. To correct these faulty cond1 tions we have 1nvented the process of, operation under controlled humidities and desire to protect thesame by Letters Patent The importance of our development, is

shownby tests of the rate of revivification. Thus certain fouled iron oxide may be exposed to air at 20% humidity for months without revivification. The same fouled oxide exposed to air at higher humidities, however, revivifies with increasing rapidity, and at 95 humidity the complete reviviiication occurs within live minutes. If revivification in situ is practiced, however, the humidity must not be so high that precipitation of liquid moisture occurs, because the very 7 wet oxide is not soactive in' the removal of hydrogen sulfide. For this removal we prefor to use humidities of about to per cent. Thus we have found that an oxide maintained and operated at 50 to 60'iper cent humidity is very much more efficient inthe removal-of hydrogen sulfide thanis the same oxide maintained and operated at a humid y of t In the technical operation of the process the oxide, usually mixed with a iiuflin-g material, such as woodshavings, is placed in a series of boxes throughwhichthe gas passes in turn. According to'our processthe, 1111- midlties maintained on each of theseboxes,

will depend upon whether it is desired to revivify in situ or not.. If revivification in situ is not practiced, thehumidity throughout the boxes .is maintained at from 45 to, 60 per cent approximately, This is most conveniently done by reducingthe temperature of the gasleaving the condensers to a point sufficiently low to insure condensation of the excess water vapor. Thus if the oxide boxes are to operate at a temperature of 80 F., the

gas leaving the condenser may becooled to.

approximately 60 FL and then is reheated to ,the operating temperature or the oxideis maintained at the desired temperature by circulating warmer water through coils embedded in the boxes. Since the gas leaving the firstbox has increasedboth in temperature line and revivified either by passing through and simultaneously revivifying fouled iron oxide which consists in admlxing oxygen wlth the gases to be purified. and controlling the humidity of the mixture at an intermediate value between 70 and 95 per cent while passing the mixture over the iron oxide, whereby sulfur is retained and water is eliminated by the fresh iron oxide, and sulfur is set free and water is absorbed by the fouled iron oxide.

VVILBERT J. HUFF. C. GORDON M'ILBOURNE.

the box air or other oxygen containing gas mixtures humidified to approximately 90 100 per cent, or it may be removed from the box, spread out and exposed to ahumid oxygen-containing gas. 7

Vhen revivification in situ is practiced, we may strike a balance between the humidity required for thebest fouling operation'and that required for the bestrevivification. Under these conditions we operate at an intermediate humidity of some 70 to 85' per cent. WVhen the system contains four or more boxes, however, we prefer to operate each of the boxes of the series so asto favor the reaction which we wish to have predominate in that box. Thus we may prefer to have the first box function chiefly as a remover 'of'hydrogen sulfide in which case weadjust the temperature and water vapor content to give a humidity of from 5L5 to 60 per centin this box. The second and third boxes may be chiefly undergoing revivification, in which case we may adjust the temperature and water vapor condit ons to give approximately 90 to 95 per cent, while the last box, used for the removal of the last traces ofhydrogen sulfide may be adjusted for a humidity of w from 45 to 60 per cent. p v.

Having thus fully described our invention we claim:

1. The process of removing hydrogen sulfide from gases by reaction with solid material containing iron oxide which consists in passingv the gasesv over said solid material while the humidity of the gases is controlled at constant fixed'points between 45 and 95 percent. i i

2. .The process of removinghydrogen sulfide from gases which consists in passing the gases over solid material, containing iron oxide while the humidity of the gases is maintained at from 45to per cent whereby sulfur is retained by the solid material and water vapor is eliminated.

The step in'the process of removing-11y I drogensulfide fromgases by reaction with solld'material containing iron oxide which consists in revivifying the suliied iron oxide material'by passingover said material an oxygen. containing gas bearing suflicient water vapor togive constant fixedfhi'gh humidities below 95 per cent.

4. The process of removinghydropen sul- 'fidefrom gases by react ion'with iron oxide 

